This invention relates generally to fork lift trucks. More specifically, the present invention relates to an automated mechanism to fold and unfold lift truck forks in response to movement of a carriage relative to a supporting mast in a fork lift mechanism.
Fork lift trucks are used by a wide variety of industries. They are one of the most common pieces of equipment used for material handling. Virtually all commodities are stacked on pallets at some point in their manufacturer or distribution and handled by fork lifts. Sometimes fork lifts are carried by delivery trucks to unload their cargos. Such is the case in the sod industry. When fork lifts are carried by trucks it is necessary to fold the forks in order to meet vehicle code and safety requirements.
A typical fork lift mechanism includes a generally vertical mast pivotally attached to the front of the fork lift truck and connected to one or more hydraulic rams which control the angle of inclination of the mast relative to a vertical plane. A carriage is slidably supported by the mast and a hydraulic mechanism is utilized to selectively raise and lower the carriage. The carriage will typically include an upper rail which supports a pair of L-shaped forks. In this regard, a fork mounting sleeve is provided at an extreme end of each L-shaped fork. The upper rail extends through the fork mounting sleeves so that the forks may pivot thereon as well as slide laterally. In normal use, a fork back extends downwardly from the fork mounting sleeve and then a fork tine extends horizontally outwardly from the carriage, generally perpendicularly from the fork back. The spacing between the forks may be adjusted by simply sliding the forks on the upper rail to the desired position.
In order to fold the forks in preparation for transporting the fork lift truck, a number of steps requiring considerable physical strength are necessary. By way of example, each of the forks typically must be slid to the respective extreme outside ends of the upper rail. When so positioned, each fork must be lifted and pivoted about the upper rail approximately 180.degree. into a transport position. This process is quite difficult for an individual considering that a fork may weigh seventy-five pounds. As an alternative procedure, fork lift operators have also utilized a raised horizontal surface, such as the bed of a flat bed truck, to assist with the fork lift folding process.
During transport of the fork lift truck, the forks in the folded position extend upwardly from the upper rail and rest on brackets provided on each side of the mast. To unfold the forks, each must be manually pulled forward so as to pivot about the upper rail, and then be restrained from falling down onto the carriage. Again, this requires substantial physical effort, and some fork lift operators have developed techniques for utilizing a raised horizontal surface, such as that provided by a flat bed truck, to assist in the process and minimize the amount of manual labor required. Nevertheless, whether the forks are strictly manually folded and unfolded, or advanced folding and unfolding techniques are utilized, multiple steps and considerable physical strength are prerequisites for completing the task.
Accordingly, there is a need for a simple automated mechanical system capable of folding and unfolding forks for transport and operation. Preferably such an automated system would utilize the fork lift's existing hydraulics and be fully actuable from the driver's position on the fork lift truck. Additionally, such an automated mechanical system and related process is needed which may be adaptable to a wide variety of fork lift trucks, and which is easy to maintain and operate. The present invention fulfills these needs and provides other related advantages.